replaced rear der

Callistus Valerius said:

Had a mysterious problem fixing a friend's bike. When I replaced his
rear der with a new 105 rear der, the problem of the der cage hitting the
spokes was solved. Did all the typical tune up dozens of times (the low
setting adjusted numerous times with same outcomes), but could not use the
large cog and small ring without the cage hitting the spokes. The only
adjustment that would stop the spoke hitting, was where you couldn't use the
large cog. The der hanger was not bent. Looking at the rear der I pulled
off, the cage does not look bent, kind of a mystery why the new one would
work, and the old one wouldn't. The pivots seem a little bit more worn than
the new one, but I can't see why that would make a difference. Changed
wheels, same outcome with old der. He thinks when he changed a rear flat,
he didn't get the wheel all the way in, and that's how he bent it. Bent it,
but where? Any ideas?

If you used a hanger alignment tool to verify the hanger was not bent
(it isn't always visible to the naked eye), then my guess would be
either the pulley cage was slightly bent/twisted and/or the pivot pins
in the derailleur were worn enough that there was enough slop in the
mechanism that made it ride closer to the spokes.

I have seen someone damage a derailleur once by improper re-insertion
into the frame. The spokes "grabbed" a small section of the cage next
to the upper pulley and twisted the derailleur.

HTH,

Greg Wood

Quoted message said:

Callistus Valerius said:

Had a mysterious problem fixing a friend's bike. When I replaced his
rear der with a new 105 rear der, the problem of the der cage hitting

the

Quoted message said:

Quoted message said:

spokes was solved. Did all the typical tune up dozens of times (the low
setting adjusted numerous times with same outcomes), but could not use

the

Quoted message said:

Quoted message said:

large cog and small ring without the cage hitting the spokes. The only
adjustment that would stop the spoke hitting, was where you couldn't use

the

Quoted message said:

Quoted message said:

large cog. The der hanger was not bent. Looking at the rear der I

pulled

Quoted message said:

Quoted message said:

off, the cage does not look bent, kind of a mystery why the new one

would

Quoted message said:

Quoted message said:

work, and the old one wouldn't. The pivots seem a little bit more worn

than

Quoted message said:

Quoted message said:

the new one, but I can't see why that would make a difference. Changed
wheels, same outcome with old der. He thinks when he changed a rear

flat,

Quoted message said:

Quoted message said:

he didn't get the wheel all the way in, and that's how he bent it. Bent

it,

Quoted message said:

Quoted message said:

but where? Any ideas?

If you used a hanger alignment tool to verify the hanger was not bent
(it isn't always visible to the naked eye), then my guess would be
either the pulley cage was slightly bent/twisted and/or the pivot pins
in the derailleur were worn enough that there was enough slop in the
mechanism that made it ride closer to the spokes.

I have seen someone damage a derailleur once by improper re-insertion
into the frame. The spokes "grabbed" a small section of the cage next
to the upper pulley and twisted the derailleur.

HTH,

Greg Wood

I think you're right. I guess I could put the old der on another bike
to see if it was the cage/der pivots, or the hanger. But you're right it's
hard to tell by eye, which one is bent, but I'm guessing it's the cage/der.